Hitherto, polyether compounds such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc., have been widely used as raw materials of resin such as polyurethane, coatings, adhesives, molding materials, ect.
Many of these polyether compounds have a hydroxyl group at the end thereof, which causes a problem in that the scope of application is restricted in the case of using them as raw materaisl for resins. For the purpose of overcoming this problem, polyether compounds having an allyl group at the terminal portion thereof, which are prepared by polymerizing the glycidyl group of allyl glycidyl ether, and polyester compounds having a vinyl group at the end which are prepared by thermal decomposition of polypropylene glycol, etc., have been used. However, many resins obtained using these compounds are insufficient in hardness and strength, though they have excellent flexibility, because the molecular structure of these compounds is straight chain.
Epoxy resins which have been widely used include epi-bis type epoxy resins produced by reacting bisphenol A with epichlorohydrin. These resins have advantages that various products are obtained in a state of liquid to solid and they can be cured at room temperature with polyamines because reactivity of epoxy resins is high. However, cured products thereof have faults in that the weatherability is inferior, electric properties such as anti-tracking property, etc., are inferior, and the heat distortion temperature is low, although they do have desirable characteristics of good water resistance and strength. In recent years, particularly, epoxy resins prepared by reacting phenol resin with epichlorohydrin have been used as resins for encapsulating VLSI (very large scale integrated circuit), etc., but chlorine contained in the resins, typically in amounts of several hundred ppm, causes the problem of deteriorating the electric properties of electronic devices.
Epoxy resins having excellent electric properties and heat resistance which do not contain chlorine are known, such as certain alicyclic epoxy resins. These have been produced by an epoxidation reaction of a compound having a 5- or 6-membered cycloalkenyl structure. The epoxy group in these resins is the so-called inner epoxy group, and curing is usually carried out with acid anhydrides by heating. However, since reactivity is low, they cannot be cured with polyamines at room temperature. Therefore,, use of the alicyclic epoxy resins is restricted to a very narrow scope.
As alicyclic epoxy resins, those having a structure represented by (IV) or (V) have been industrially produced and used. ##STR8##
(VI) has been used as a heat resisting epoxy diluent, because of having a very low viscosity, but it has high toxicity and causes problems of poisoning by skin contact.
(V) contains only amounts of impurities and has low color hue, and cured products produced therewith have a high heat distortion temperature, but its use involves problems of inferior water resistance due to the ester bond.
In addition, because both (IV) and (V) are liquid epoxy resins having a low viscosity, it is impossible to apply molding systems for solid epoxy resins, such as transfer molding, etc., to them.